Two experiments are used to demonstrate how light travels in straight lines. In the first example, the presenter arranges three pieces of card, with holes in, in an uneven line. The light stops and cannot travel through all three cards. When she arranges the holes in a straight line, the light can travel through. In the second example, a light source is shone onto a shiny and uneven surface. We see how the light still travels in a straight line, but scatters and reflects in different directions.
This clip could be used when exploring how light travels. After having shown the clip, hand out little mirrors and torches, asking the children to work in pairs. One is holding the torch, the other one is reflecting the light, changing the angle of the mirror to see where the light falls. Teachers could repeat the experiment shown in the clip, providing three cards with holes in them. First ask the children to let the light travel in a straight line through the holes. Then invite them to try to direct the light in an angle using their mirrors. The clip could be used in a lesson introduction to illustrate the teaching point that light travels in a straight line. The two experiments shown are very simple and easy for a teacher to set up. The teacher could carry them out at the beginning of the lesson and the clip could be shown in a plenary session to reinforce the teaching point.